Keep an eye out for $1 Federal Reserve notes that have seven repeating digits in a row. For instance, numbers like 09999999, 18888888, 19999999, and more. These bills are considered quite unique and valuable!
Another special type of $1 Federal Reserve note is the one that has seven of the same digit. Look for numbers like 00010000, 00090000, 90999999, and many others. These bills are highly sought after by collectors!